Crossed-coil rotating-magnet measuring instrument

ABSTRACT

In a crossed-coil rotating-magnet measuring instrument having an approximately cylindrical core developed as winding form, a first and second coil are wound crossed one above the other. The second coil is necessarily arranged over the first coil in the regin of the ends of the winding form and thus has a greater height of winding than the latter. Within the core there is also provided a rotating magnet whose pointer shaft is extended out of an extension of the core. In order to reduce the linearity error of this measuring instrument and to permit a reading over several quadrants, spacer means are provided on the core for guiding turns of the coil spaced from the extension of the core around the latter in a rectangular plane in each case. In combination with this, the core is developed with a large diameter in the winding region of the first coil, said diameter being of such a value with respect to the diameter of the winding region of the second coil that the average lengths of the turns of the two coils are the same.

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a crossed-coil rotating-magnet measuringinstrument.

Crossed-coil rotating-magnet measuring instruments have an approximatelycylindrical core, developed as a winding form, on which a first and asecond coil are wound crossed one over the other, the second coil beingarranged in the region of the ends of the winding form over the firstcoil and thus having a greater height of winding than the latter, therebeing mounted in the core a rotating magnet whose pointer shaft isextended out of an extension on the core.

Such known cross-coil rotating-magnet measuring instruments are used forvarious measuring and indicating purposes, for instance for themeasurement of the level of filling of containers or temperature or elseas voltmeter or ammeter.

The known crossed-coil rotating-magnet measuring instruments have a coreused as winding form and within which the rotating magnet is turnablymounted. From one end of the substantially cylindrical core thereprotrudes an extension within which the rotating-magnet shaft isarranged and passes into the pointer shaft which is extended out of theextension. Upon the winding of the core, the turns of the coils aredeformed in the region of the extension of the core and thus do not liein a flat rectangular winding plane. Since furthermore the two coilswhich cross each other on the core must necessarily be wound one abovethe other in the region of the ends of the core, the heights of windingof the two coils are different.

It has been found that with known crossed-coil rotating-magnet measuringinstruments of the aforementioned type there can only be obtained anglesof deflection which are slightly above 90°. If only the first quadrantessentially is utilized in these measuring instruments, calibration tothe desired final value of the full deflection can be effected byadjustment of at least one voltage signal which acts on one of the twocoils. However, it is not readily possible to use such crossed-coilrotating-magnet measuring instruments for reading over several quadrantssince a displacement of the final value in the first quadrantnecessarily results in a displacement in opposite direction in the thirdquadrant.

It is an object of the invention so to improve a crossed-coilrotating-magnet measuring instrument of the aforementioned type that itcan be used with sufficient accuracy for reading over several quadrantsand in particular up to the third quadrant. Difficulties resulting froma calibration by means of adjustment of a voltage signal in a coil areto be avoided in this connection.

SUMMARY OF THE INVENTION

According to the invention, spacer means (bars 11-14) are arranged onthe core (1) and guide turns of the coils (9, 10) spaced from theextension of the core around the latter, in each case a rectangularplane, and that the core has, in the winding region (7) of the firstcoil (9), a diameter which is so increased as compared with the diameterof winding region (8) of the second coil (10) that the average lengthsof turns of the first and the second coil are equal.

By the combination of these features an error of linearity of thepointer deflection over several quadrants is substantially reduced sothat voltage control of both coils with two voltage signals whosemaximum values are equal is possible. In this way it is avoided that theerror in the third quadrant is increased by a calibration in the firstquadrant or vice versa.

The spacer means provided as combination feature are preferablydeveloped as elongated bars (11-14) which are embedded in thecylindrical wall region of the core and are at least as wide as theextension point (2) of the core where the pointer shaft is brought out.

By the elongated bars, which preferably extend into the ends of the coreand are rounded at the ends as well as on their tops, there is assured aparticularly reliable guiding of the winding wire which does notinterfere with the winding process.

BRIEF DESCRIPTION OF THE DRAWING

With the above and other objects and advantages in view, the presentinvention will become more clearly understood in connection with thedetailed description of a preferred embodiment, when considered with theaccompanying drawing, of which:

FIG. 1 is the core in a top view of the side from which the extensionextends;

FIG. 2 is a side view of the core; and

FIG. 3 shows a pointer shaft extending from an extension of the core ofFIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

From FIGS. 1, 2 and 3 there can be noted the substantially cylindricalshape of the core, designated generally as 1, used as winding form. Anextension for a pointer shaft extends out of the point 2 from one end ofthe core. By guide elements 3 to 7 on the periphery of the cylindricalform of the core the latter is subdivided into two winding regions 7 and8. The winding region is intended for the winding of the core with afirst coil 9 over which a second coil 10 is wound, crossed 90°, in thesecond winding region.

As indicated in FIG. 1, the diameter of the core in the winding region 7is greater than in winding region 8, in such a manner that the greaterheight of winding of the second coil 10 as compared with the first coil9 is compensated for, i.e. the average length of turn for both coils 9and 10 is the same. From this there furthermore result for identicalsignal voltages in the two coils an identical number of turns and, inthe case of the same diameter of wire, the same resistance of the twocoils.

In connection with the above measures there should also be noted thestructural measure which consists therein that by four elongated bars 11to 14 it is seen to it that the windings of the coils are not pressedaway out of the region of the extension at the point 2 but are guided inflat rectangular planes. The flat rectangular planes figuratively cutthe core in longitudinal planes outside of the central longitudinal axisof the core. The elongated bars divide each of the two winding regions 7and 8 into two individual winding regions of equal size. Thereforeconditions symmetrical to two planes are present for the winding of thecore, namely with respect to the central planes which extend, on the onehand, through the bars 13 and 11 and, on the other hand, through thebars 12 and 14. These central planes are designated 15 and 16.

The rounding of the bars 11 to 14 at the ends and on their outersurfaces can be noted in detail from the drawing. This shape canfacilitate the winding process and in addition assist in avoiding damageto the wire.

It has surprisingly been found that in the case of a crossed-coilrotating-magnet measuring instrument of the type described the linearitycan be improved by, for example, 500%.

We claim:
 1. A crossed-coil rotating-magnet measuring instrumentcomprising an approximately cylindrical core configured as a windingform, on which a first coil and a second coil are wound crossed one overthe other, the second coil being disposed in the region of ends of thewinding form over the first coil and thereby having a greater height ofwinding than the latter, and there being mounted in the core a rotatingmagnet having a pointer shaft extending out of an extension on the core,the instrument including an improvement comprisingspacer means disposedon the core for guiding turns of the coils in a planar configurationalongside the extension of the core, each turn of the coil lying in arectangular plane, and wherein said core is asymmetrical, asymmetry ofthe core being characterized by an enlarged diameter in a winding regionof the first coil, the diameter of the core being enlarged as comparedwith the diameter of a winding region of the second coil so as toequalize the average lengths of turns of the first coil and the secondcoil, thereby improving linearity in measurements employing rotations ofsaid magnet over a plurality of quadrants.
 2. The cross-coilrotating-magnet measuring instrument according to claim 1, whereinsaidspacer means are elongated bars extending along a diametrical plane ofthe core from a cylindrical wall region of the core, and are at least aswide as said extension.